In a microwave communications network, wherever a transmission path (link) is to exist, accurate antenna path alignment is required to insure proper communications. Typically, links are between tower-mounted antennas up to 25 miles apart, and an initial alignment process requires tower crews to physically align the antennas using sophisticated test equipment to monitor the results. Using today's techniques, initial alignment can be off-path by several degrees to either side of the target antenna, resulting in the target being in a null or side lobe of the pattern of the antenna being aimed.
More specifically, one current practice of initial alignment of tower-mounted antennas requires that the two antennas be installed on their towers to provide a signal link for power measurements. A compass bearing to the distant end is taken and the antenna is visually aimed at a ground-based reference along that direction, typically a marker or a natural reference such as a tree. Radios are installed at each site and used to optimize the path.
Some antenna alignment methods use out-of-network radio devices, which permit tower installation crews to perform the alignment process before network radios are installed. One example is the Path Align-R™ test set from XL Microwave. Two identical test sets are used, one at each tower site. Each test set drives its respective antenna directly, while receiving the signal from the other test set. During alignment, the test sets provide continuous duplex voice communication over the antenna link, allowing the two technicians to communicate with each other. Both units indicate the received path loss, and each antenna's azimuth and elevation is physically adjusted, until minimum loss (maximum alignment) has been reached.